Go SHM API to read simple data with size from SHM name

tools/utils/shm/shm.go

@@ -5,13 +5,17 @@ package shm
 import (
 	"crypto/rand"
 	"encoding/base32"
+	"encoding/binary"
 	"errors"
 	"fmt"
+	"io"
 	not_rand "math/rand"
 	"os"
 	"strconv"
 	"strings"
 
+	"kitty/tools/cli"
+
 	"golang.org/x/sys/unix"
 )
 
@@ -109,3 +113,69 @@ func truncate_or_unlink(ans *os.File, size uint64) (err error) {
 	}
 	return
 }
+
+func read_till_buf_full(f *os.File, buf []byte) ([]byte, error) {
+	p := buf
+	for len(p) > 0 {
+		n, err := f.Read(p)
+		p = p[n:]
+		if err != nil {
+			if len(p) == 0 && errors.Is(err, io.EOF) {
+				err = nil
+			}
+			return buf[:len(buf)-len(p)], err
+		}
+	}
+	return buf, nil
+}
+
+func read_with_size(f *os.File) ([]byte, error) {
+	szbuf := []byte{0, 0, 0, 0}
+	szbuf, err := read_till_buf_full(f, szbuf)
+	if err != nil {
+		return nil, err
+	}
+	size := int(binary.BigEndian.Uint32(szbuf))
+	return read_till_buf_full(f, make([]byte, size))
+}
+
+func test_integration_with_python(args []string) (rc int, err error) {
+	switch args[0] {
+	default:
+		return 1, fmt.Errorf("Unknown test type: %s", args[0])
+	case "read":
+		data, err := ReadWithSizeAndUnlink(args[1])
+		if err != nil {
+			return 1, err
+		}
+		_, err = os.Stdout.Write(data)
+		if err != nil {
+			return 1, err
+		}
+	case "write":
+		data, err := io.ReadAll(os.Stdin)
+		if err != nil {
+			return 1, err
+		}
+		mmap, err := CreateTemp("shmtest-", uint64(len(data)+4))
+		if err != nil {
+			return 1, err
+		}
+		defer mmap.Close()
+		binary.BigEndian.PutUint32(mmap.Slice(), uint32(len(data)))
+		copy(mmap.Slice()[4:], data)
+		fmt.Println(mmap.Name())
+	}
+	return 0, nil
+}
+
+func TestEntryPoint(root *cli.Command) {
+	root.AddSubCommand(&cli.Command{
+		Name:            "shm",
+		OnlyArgsAllowed: true,
+		Run: func(cmd *cli.Command, args []string) (rc int, err error) {
+			return test_integration_with_python(args)
+		},
+	})
+
+}

tools/utils/shm/shm_fs.go

@@ -113,7 +113,7 @@ func create_temp(pattern string, size uint64) (ans MMap, err error) {
 	return file_mmap(f, size, WRITE, true, special_name)
 }
 
-func Open(name string, size uint64) (MMap, error) {
+func open(name string) (*os.File, error) {
 	ans, err := os.OpenFile(file_path_from_name(name), os.O_RDONLY, 0)
 	if err != nil {
 		if errors.Is(err, fs.ErrNotExist) {
@@ -123,5 +123,23 @@ func Open(name string, size uint64) (MMap, error) {
 		}
 		return nil, err
 	}
+	return ans, nil
+}
+
+func Open(name string, size uint64) (MMap, error) {
+	ans, err := open(name)
+	if err != nil {
+		return nil, err
+	}
 	return file_mmap(ans, size, READ, false, name)
 }
+
+func ReadWithSizeAndUnlink(name string) ([]byte, error) {
+	f, err := open(name)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	defer os.Remove(f.Name())
+	return read_with_size(f)
+}

tools/utils/shm/shm_syscall.go

@@ -151,3 +151,13 @@ func Open(name string, size uint64) (MMap, error) {
 	}
 	return syscall_mmap(ans, size, READ, false)
 }
+
+func ReadWithSizeAndUnlink(name string) ([]byte, error) {
+	f, err := shm_open(name, os.O_RDONLY, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	defer shm_unlink(f.Name())
+	return read_with_size(f)
+}